This invention relates to an apparatus for the cutting of apertures in the lining of existing conduits and pipelines and, more particularly, is concerned with cutting improved connections between intersecting lateral pipelines and lined main pipelines, such as underground sewers.
In accordance with the established Insituform.RTM. Process for lining underground pipelines or passageways, a flexible tubular liner of a resin-absorbent material that is impregnated with a curable resin is everted into the passageway. The resin-impregnated liner, while still flexible, is held against the interior surface of the pipeline or passageway by the inverting fluid, and the resin is allowed to cure. This process is described in U.S. Pat. No. 4,064,211 and No. 4,581,085, the contents of which are incorporated herein by reference. Another process for lining existing conduits involves installation of a fold-and-formed rigid pipe. As described in U.S. Pat. No. 4,867,921 and No. 5,368,809, the contents of which are incorporated herein by reference, a thermoplastic liner is heated to render it pliable and is inserted into the pipeline in a reduced form. The deformed liner is subsequently re-rounded and allowed to harden.
The result of both processes is that the pipeline or conduit is lined with a rigid lining. These methods are extremely successful, but after installation the lining extends also across the apertures for side or branch connections, such that any side-connecting or lateral pipes that previously led into the main pipeline become blocked. These side or lateral connections must be reestablished in order for the pipeline to function as it did prior to the lining operation. As can be appreciated, the reestablishment of the side connections will entail cutting away a portion of the lining that covers each side connection, and the invention provides a device for performing this reopening in a neat, effective and efficient manner.
Because the pipelines lined are often located under ground, the matter of reestablishing the side connections involves some difficulty. Currently, equipment that is used for the reestablishment of these connections are cutters operated from a remote location and are designed to cut away the portion of the lining covering each side connection. The cutter typically includes a unit, called a "work unit," that moves along the inside of the main passageway with a TV camera mounted to the front of the work unit and that is controllable and viewable from above ground level to assist in locating the lateral connection and positioning the work unit relative thereto. The work unit also typically includes a cutting device mounted thereon.
Various cutting devices are currently in use. These cutting devices are provided with a rotary cutter bit that is rotated about an axis substantially radial to the pipe in which it operates. The cutter bit is adapted to be moved circumferentially in an angular fashion about an axis that is longitudinal of the pipe. The cutter bit can be moved longitudinally along the length of the pipe and, once the work unit is in position, is moved radially outward and inward with respect to the surface of the pipe. In addition, in some instances, the cutter bit may also be tilted forward or backward about an axis that is radial to the pipe. These various movements are provided in order to enable the cutter bit to follow the angle at which the side connection meets the main pipeline and to follow the contour of the opening that is covered by the lining material. This assures the reestablishment of the connection between the lateral and main pipe. The movements of the cutter head may be controlled by means of suitable motors, such as pneumatic, hydraulic or electric motors. Electric motors preferably are stepper motors whose movement can be controlled by digital signals. In each case, the motor is securely mounted in the cutter assembly.
Because the various cutting devices are bound to have different degrees of accuracy and precision, the result is an inexactness of the extent to which the contour cut through the pipe liner meets the aperture for the side-connecting pipe. There typically remain "shark's teeth" or "ledges" or rough edges of lining material overlapping the original opening sides that may be a means for trapping debris and waste material and may impede the connection with the main passage, in some cases leading to the eventual obstruction of the side passage by blockage. Therefore, it is desirable to trim the edges of the liner about the opening cut therethrough. One way of trimming the edges of the aperture is by using a toothed side portion of the cutting bit, which, when rotated at a high rate of speed against the edges of the aperture, grinds away and smooths the roughened edges created by the cutting bit. Unfortunately, however, the same precision and accuracy problems that plague the cutting bit in cutting also plague the cutting bit in trimming.
A more preferred device for trimming the aperture cut through the liner is a smoothing bit, such as a wire brush, because it has proven to be much more effective in smoothing any rough edges or ledges in the lining material, thereby allowing smoother flow of fluids through the aperture. A wire brush has a larger diameter than a cutter bit and requires less movement to smooth the rough spots. Additionally, a wire brush is more discriminating in that it will trim the rough edges in the polymerized synthetic resin of the liner without damaging or otherwise affecting the hard material, such as clay, cast iron or the like, of the underground conduits. Generally, such a wire brush is a separate attachment to the work unit and contains its own motor for movement of the brush in a manner similar to those discussed above with respect to the cutting bit.
A significant problem with using a wire brush for trimming the apertures cut through the liner is using a brush requires a second positioning operation of the work unit. Typically, the work unit having a TV camera and a cutter is removed from the pipeline after the opening in the lining is cut. The cutter bit is removed and the wire brush is placed in its stead, and the work unit is pulled back through the existing pipeline for trimming of the edges of the apertures just cut through the liner by the drill bit. Unfortunately, this repeat operation is inefficient in terms of time, cost and labor.
It is, therefore, desirable to provide a device that would allow cutting of the aperture and trimming of edges at the junction of the main pipeline and side connection in one operation.